Southern California -- this just in

San Onofre nuclear plant out of service for the summer

The top official at Edison International said Thursday that the troubled San Onofre nuclear plant will remain out of service through the summer.

The plant has been shuttered since Jan. 31 while officials probe the extent and cause of unusual wear on tubes that carry radioactive water in the plant's newly replaced steam generators.

The Nuclear Regulatory Commission has ordered the plant to stay offline until Edison can identify the exact cause of the wear and how to fix it.

Ted Craver, chief executive officer of Edison, the parent company of plant operator Southern California Edison, said as the process stands, the earliest that the Unit 2 reactor could restart would be the end of summer, and Unit 3 may take longer. Most of the troubling wear was found in Unit 3.

"I don't see how we could submit [a restart plan] to the NRC before the end of July, and their process is maybe another month, so that's the end of August," Craver said.

He said the call on when it is safe to restart the plant will be a "huge decision."

"I'm not sure there's going to be a bigger decision I make in my time as CEO here," he said.

Edison officials believe that the most concerning wear is happening because the rate of steam flow among the tubes is causing excessive vibration, leading the tubes to rub against each other. But officials still have not pinpointed exactly what led to that issue.

Craver said the steam generators, installed to replace the old, aging equipment, were designed to prevent such vibration but "the implementation of the design doesn't appear to be meeting the specification."

To date, 1,317 tubes in the plant's two working reactor units have been taken out of service, 510 in Unit 2 and 807 in Unit 3. About one-third of those were plugged because of excessive wear and the others as a preventive measure, Craver said.

When running at full capacity, San Onofre supplies about 2,200 megawatts of power and makes up 19% of the power provided to Edison customers. With contingency plans in place, officials said Southern California should be able to get through the summer without power shortages under all but the most extreme circumstances.

A pair of mothballed generating units in Huntington Beach have been taken temporarily out of retirement, transmission upgrades were accelerated, and officials are offering incentives for customers to conserve power.

The short-term plan to restart the units could involve running at lower power to decrease the rate of steam flow. In the longer term, Craver said the options could range from adding supports for the tubes to replacing the steam generators entirely.

The steam generator problems and other issues at the plant have led some environmental groups and local residents to say the plant can't be operated safely and to call for it to be decommissioned.